The present invention relates generally to the production of casting molds, and more particularly to a system whereby at least two pattern plates are arranged with their partern surfaces in opposing relationship to define a cavity within which a mold section is formed. It has been heretofore known to fill a molding cavity defined between the two opposing walls of a pair of pattern plates with clay-bonded molding sand precompressed by means of compressed air, and subsequent to the filling operation to compress the molding sand to form a mold. After one of the pattern plates has been retracted and swung out of position, the mold thus produced is ejected from the molding cavity by the other pattern plate and it is pushed onto a mold row and pressed upon. It is possible to insert into the mold thus formed cores which either bear on the mold base or which are suspended in the mold. After the ejecting pattern plate is retracted and the pattern plate which has been swung out of position is returned to its original location, a new mold is produced in the above described cycle and at the same time the mold is cast on end at a sufficient distance from the molding machine. After the iron in the cast molds has cooled off sufficiently, the latter are dropped at the end of the mold zone onto an emptying grid.
A disadvantage of this method is that the mold surface thus produced can only be covered to a minor extent with patterns, because of the ferrostatic pressure and because of the necessity for casting the molds on end. Another disadvantage resides in the fact that, in molds cast on end, an additional part of the mold surface can not be used for the extended casting system. Another disadvantage is that the cooling time of the molds between casting and emptying is limited by the maximum permissible length of the mold stack. Still another disadvantage, which limits the use to mass castings, results from the fact that expensive pattern plates are necessary for carrying out this method. The greatest disadvantage, however, arises in the production of castings whose material analysis depends on wall thickness, such as grey cast iron, spheroidal cast iron and the like. For each of the plants utilizing these techniques, liquid metal must be available at any time for the material-analysis, because the molds thus produced are not storable. This direct interdependence between a molding plant of relatively low capacity and the smeltery leads therefore in practice to the requirement for a plurality of smaller smelting units.
Furthermore, there is presently known a plant (British Patent No. 1,066,833) which produces in one operation from plastic-bonded sand a lower mold section, an upper mold section and the respective cores, and which subsequently joins these sections mechanically in a ready-to-cast mold. This production method has the disadvantage that it requires relatively large quantities of plastic-bonded molding sand, which is expensive. Furthermore, like the first described method, the molds can only be cast on end, thereby resulting in a lower metallic yield and high ferrostatic pressure. In addition to the above described disadvantages, these plants have an extremely low output.
The development of recent foundry techniques has generally been in the direction of producing molding and casting plants having a higher mold face output per hour. Furthermore, the tendency is to increase the utilization of the mold faces beyond presently known values by covering the pattern plates as extensively as possible with the molding pattern. Such molding and casting plants achieve their optimum production capacities only if the working range of these plants, as far as length, width and height of the models is concerned, can be extended beyond presently known dimensions. If such molding and casting plants are used for the production of general jobbing items, it will be found that a residual order of small castings of suitable quality can no longer be economically produced in these plants. Such small castings must generally be produced in orders of relatively large quantity. Also, such small castings must have narrower mass tolerances and better finishes than can be produced in high-capacity molding and casting plants which utilize plastic-bonded sand. Furthermore, it will be found that thin-walled castings cannot be produced economically on heavy duty machines together with large castings, because of the risk that the casting will break during separation from the mold or during cleaning operations.
Additionally, as is commonly known, a jobbing foundry must maintain in stock a great number of pattern plates which are seldom used but which are required for the production of spare parts or other small orders. In many instances, such orders cannot be accepted by a high-capacity plant because of the time required for changing the pattern plates which, in a high-capacity molding or casting plant, is much too expensive.
The production of flat, low castings of relatively great length and width, such as for example, side shields for textile machines and similar equipment, requires special molding machines. These are mostly high-pressure squeezers which work with low molding boxes, reinforced with closely arranged traverses. These special machines are necessary because of the accuracy required of the castings, but their capacity is poorly utilized due to the limited number of orders usually received.
Thus, it is an object of the present invention to alleviate the above-mentioned drawbacks in the production methods available to a modern foundry.